Fly Predators are a natural alternative to fly sprays and chemicals. Fly Predators are beneficial bugs that control flies naturally. Fly Predators stop pest flies by taking over the fly’s cocoon, thereby killing immature pest flies. These tiny insects are the natural enemy of flies, but never bother people or animals. You’ll likely never see them, but you will see their results. Simply sprinkle Fly Predators near all manure areas every four weeks beginning in spring and continuing through summer. Fly Predators are effective and easily applied within a few minutes each month. The key is to begin early in the season before pest flies become heavily populated.